Since about 1905 it has been known to use tissue traction for stretching parts of the body, and in approximately 1957 Neuman performed tissue expansion in practice. Traction of fingers was first described by the American investigator Cowen who, at the annual U.S. Congress of Orthopedic Surgery in 1977, spoke about stretching fingers to normal length in children who had been born with too short fingers. On the basis of his clinical work Cowen reported that blood vessels and all other tissues on the extremity are stretched, provided that the rate of traction does not exceed the rate of nerve regeneration.
Animal experiments have shown that the epidermis responds to constant expansion or tension by increasing cell division activity in the basal layer, a process which reaches a maximum rate within about 24-48 hours and typically normalizes within 6 days. These animal experiments have also shown that expansion of the dermis tends to reduce its thickness slightly. However, normalization of the thickness of the dermis following expansion has been reported after about two years.